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P Sinha

Publications and source records attributed to P Sinha.

At least 163 records · Page 9Linked to original sources
PubMed1984

Mutants of S. cerevisiae defective in the maintenance of minichromosomes.

We have isolated yeast mutants that are defective in the maintenance of circular minichromosomes. The minichromosomes are mitotically stable plasmids, each of which contains a different ARS (autonomously replicating sequence), a centrometeric sequence, CEN5, and two yeast genes, LEU2 and URA3. Forty minichromosome maintenance-defective (Mcm-) mutants were characterized. They constitute 16 complementation groups. These mutants can be divided into two classes, specific and nonspecific, by their differential ability to maintain minichromosomes with different ARSs. The specific class of mutants is defective only in the maintenance of minichromosomes that carry a particular group of ARSs irrespective of the centromeric sequence present. The nonspecific class of mutants is defective in the maintenance of all minichromosomes tested irrespective of the ARS or centromeric sequence present. The specific class may include mutants that do not initiate DNA replication effectively at specific ARSs present on the minichromosomes; the nonspecific class may include mutants that are affected in the segregation and/or replication of circular plasmids in general.

Chromosomes↗
PubMed1984

Effects of couple stresses on the blood flow through an artery with mild stenosis.

An analysis of the effects of couple stresses on the blood flow through thin artery in the presence of very mild stenosis has been carried out with the help of two nondimensional parameters, alpha (the length ratio parameter) and eta (the parameter characterizing the antisymmetric property of the couple stress tensor). It is shown that an increase in the couple stress (small value of alpha and eta), increases the resistance to the flow and the wall shear stress. These characteristics are further enhanced by the presence of the stenosis.

Arteries↗
PubMed1983

Replication in Drosophila chromosomes. X. Two kinds of active replicons in salivary gland polytene nuclei and their relation to chromosomal replication patterns.

DNA fibre autoradiography of highly polytenized nuclei in salivary glands of Drosophila nasuta larvae reveals two distinct types of active replicons. Type I replicons are longer (mean size = 64 micrometers), have a very high rate of fork migration (average rate = 0.95 micrometer/min) and generally occur in large arrays often extending over several thousand micrometers. In contrast, the type II replicons are smaller (mean size = 20 micrometers), slow replicating (average rate = 0.07 micrometer/min) and occur in short arrays containing only a few closely spaced active replicons. Evidence is presented that type I replicons are active in the early S and type II in the late S. Observations on autoradiographic labelling of partially lysed polytene chromosomes provide evidence for a lack of temporal and spatial agreement in the activation of origin points in homologous regions of the lateral polytene strands; these observations also suggest local variations in levels of polyteny within a chromosome. On the basis of this and other available information on replication in polytene chromosomes the possible roles of the two replicon types in the generation of the different 3H-thymidine labelling patterns of polytene chromosomes are discussed.

Animals↗
PubMed1983

Replication of Drosophila chromosomes. IX. Stimulation of initiation of polytene replication cycles in vitro by juvenile hormone.

A greater proportion of polytene nuclei show [3H]thymidine incorporation when third instar larval salivary glands of Drosophila nasuta are pulse-labelled after in vitro culture (3-24 h) in the presence of a juvenile hormone mimic, ZR 515. In glands chronically labelled with [3H]thymidine in the presence of ZR 515, more nuclei are seen to have entered new polytene replication cycles. Similarly, when salivary glands from larvae fed on 5-fluorodeoxyuridine to block polytene replication cycles at intersynthetic periods were cultured in vitro, new polytene replication cycles were initiated more quickly in the presence of ZR 515. These results suggest a stimulatory effect of juvenile hormone on new polytene replication cycles.

Animals↗
PubMed1981

Dosage compensation of x-chromosome activity in interspecific hybrids of Drosophila melanogaster and D. simulans.

We have used the unstable ring X-chromosome of D. melanogaster to generate XX/X0 mosaics in the hybrid progeny from crosses between D. melanogaster females and D. simulans males. The functional properties of the polytene X-chromosome(s) in salivary glands of such X0/XX mosaic hybrid larvae have been analysed by autoradiography after 3H-uridine or 3H-thymidine labelling of the glands. The simulans X-chromosome in the hybrid X0 nuclei displays typical pale staining, enlarged diameter, higher rate of transcription (nearly two times higher than each of the Xs in the XX nuclei in the same gland) and a faster completion of replication as would be the case in the original parental X0 or XY nuclei. In the hybrid XX polytene nuclei, the melanogaster as well as the simulans X functions in the same manner as in female cells of the parents. The nucleolar transcription is also equal in the hybrid XX and X0 nuclei. Thus is seems that despite the evolutionary diversification between these two species, the regulator system which brings about the dosage compensation of X-chromosome activity has been conserved.

Alleles↗
PubMed1978

Bilharzial portal fibrosis: an important cause of portal hypertension.

Thirty consecutive cases of portal hypertension seen in a surgical unit in Lusaka, Zambia, are reported. Of these cases 70% were due to portal fibrosis caused by Schistosoma mansoni infestation. Portacaval shunting was undertaken in most cases. Patients with portal fibrosis responded more favourably to portal decompression than did patients with cirrhosis. It is probable that the condition is more common than is generally reconigzed in areas where S. mansoni infestation is endemic.

Adolescent↗
PubMed1977

Ethanol and spinal presynaptic inhibition in man.

Ethanol, 0.65 gm per kilogram of body weight, was administered orally to 6 normal subjects. The mean blood ethanol levels ranged from 0.74 to 0.99 gm per liter over a subsequent 40-minute testing period. The proportion of the soleus motoneuron pool activated by the Achilles tendon reflex was reduced. Vibratory inhibition of the monosynaptic reflex was used as an estimate of spinal presynaptic inhibition. It was unaffected by ethanol.

Adult↗
PubMedDate not supplied

A 61-kb ring chromosome shows an ARS-dependent increase in its mitotic stability in the mcm2 mutant of yeast.

We have studied the effects of ARS addition and deletion on the maintenance of a 61-kb ring derivative of chromosome III in a minichromosome maintenance mutant of yeast carrying the mcm2-1 mutation. When this ring chromosome, CIIIR, had either of its two strong origins deleted, the resultant chromosome showed a much greater instability in the mutant as compared to that of the wild-type strain. Integration of more ARSs improved the maintenance of CIIIR in the mutant but not in the wild-type strain. Increase in the size of CIIIR, without any ARS addition, did not improve the stability in either strain. A spontaneous revertant for improved growth at 35 degrees C also co-reverted for minichromosome and CIIIR maintenance. The results suggest that ARS malfunctioning leads to minichromosome and chromosome loss from mutant cells, affecting their growth at higher temperatures.

Adenosine Triphosphatases↗
PubMedDate not supplied

Photographs of the human face and broken projective symmetry.

The exact projective symmetry manifested in photographs is broken if the object is not flat. It has been found that front view perspectives of the human face, photographed with limited variations in camera angle (within 30 degrees) show a breaking projective symmetry sufficiently small to be considered for accurate comparison. As a practical implementation of this new approach, a computer-controlled video camera superimposition technique has been developed and demonstrated in the identification of a disguised human face.

Face↗
PubMedDate not supplied

Isoenzyme and molecular characterization of Entamoeba histolytica and Entamoeba dispar isolates from symptomatic and asymptomatic subjects.

AIM: To correlate the clinical features of amebic infections with the characteristics of Entamoeba culture isolates of stools. METHODS: Isolates from seven irritable bowel syndrome (IBS) patients, four asymptomatic cyst passers (ACP) and five patients with invasive amebic disease were subjected to hexokinase polyacrylamide electrophoresis (HK-PAGE) and their DNA subjected to restriction fragment (RF) analysis of amplified polymerase chain reaction (PCR) products. These findings were correlated with anti-amebic serology. Two axenic pathogenic strains (HM1:IMSS, NIH:200) and one xenic nonpathogenic strain (SAW1734) were used as standards. RESULTS: All isolates from IBS patients as well as ACP had slow-moving (nonpathogenic) band pattern, whereas those from patients with invasive disease had fast-moving (pathogenic) band pattern on HK-PAGE. Serological data using EIA and RF patterns of PCR-amplified genome corroborated these results. CONCLUSIONS: Our results support the view that there are two species of Entamoeba infecting humans--E. histolytica(pathogenic) and E. dispar (nonpathogenic), and HK-PAGE of culture isolates can differentiate between them.

Animals↗
PubMedDate not supplied

Ratio of alpha 1-antichymotrypsin--prostate specific antigen to total prostate specific antigen in prostate cancer diagnosis.

OBJECTIVE: To evaluate the analytical performance and diagnostic utility of prostate specific antigen (PSA) bound to alpha 1-antichymotrypsin (ACT) in serum to improve the differentiation between benign prostatic hyperplasia (BPH) and prostate cancer (PCa). METHODS: A total of 351 white men 21 to 88 years old were analysed. Serum concentration of tPSA, free PSA (fPSA) and ACT-PSA were measured in 163 untreated PCa patients (median age 66 years), 94 patients with histologically or clinically confirmed BPH (median age 65 years) and 94 men without prostate disease considered as controls (median age 54 years). The Elecsys system 2010 (Roche Diagnostics, Germany) was used for the determinations of tPSA and fPSA. The ACT-PSA assay is a new developed prototype on the ES system (Roche Diagnostics, Germany). RESULTS: The ACT-PSA assay showed reliable data of analytical performance in comparison to established assays for tPSA and fPSA. The median concentrations of tPSA (PCa: 9.22 micrograms/L, BPH: 2.28 micrograms/L, controls: 0.99 microgram/L) and ACT-PSA (7.99 micrograms/L vs. 1.63 micrograms/L vs. 0.58 microgram/L) were significantly different, respectively. The median ratios of fPSA/tPSA (PCa: 12.3%, BPH: 25.4%), ACT-PSA/tPSA (90.5% vs. 66.6%) and fPSA/ACT-PSA (14.0% vs. 38.6%) were significantly different between PCa and BPH patients. Significant differences of ratios between BPH and controls were not observed. Receiver operating characteristics analysis (tPSA up to 20 micrograms/L) for discrimination between PCa and BPH showed that the ratios fPSA/tPSA (area under the curve: 0.861) and fPSA/ACT-PSA (0.847) were significantly different from tPSA (0.663), but ACT-PSA (0.733) alone and also the ratio of ACT-PSA/tPSA (0.780) were not significantly different from tPSA (0.663). CONCLUSION: The ratio fPSA/tPSA showed the best discrimination between BPH and PCa. The single or additional determination of ACT-PSA to tPSA does not improve the differentiation between the two groups of patients.

Adult↗
PubMedDate not supplied

Immune factor and infertility.

Infertility is a common problem seen in gynaecological practice. In a significant number of cases of infertility an immune factor may be operative. In our study of 200 cases, the presence of sperm antibodies was studied in sera of both males and females. The tests used were the gelatin and tube slide agglutination tests. In the infertile group with unexplained infertility (50 couples), 16% of males and 30% of females were positive by the gelatin agglutination test, and 18% of males and 30% of females were positive by the tube slide agglutination test. There was complete absence of positive test (by both methods) in male controls, but females had positive tests for antibodies by both methods in significant numbers.

Adult↗